The present invention relates to agricultural machines such as harvesting machines or tractors, of the self-propelled automatic-steering type, and is more particularly concerned with switch mechanisms for turning the automatic steering system in such machines on and off.
Self-propelled agricultural machines provided with automatic steering have been suggested heretofore. Such machines are ordinarily provided with automatic guiding means having a sensing device operative to sense the plant rows, furrows, or other predetermined lines of reference. Such machines must also be provided with mechanisms for switching the automatic steering system off, so that the machine may be driven in a manual steering mode when desired or when necessary in the case of an emergency. Furthermore, the system should be so arranged that it is possible to switch the automatic steering on again, without excessive difficulty, when the machine is in motion. Known arrangements adapted to provide these types of operation include an operating switch which is normally situated at a convenient position near the driver's seat, so that the automatic steering system can be switched on and off as desired. This operating switch is often mounted on the steering column in the machine, directly below the steering wheel.
Arrangements of the type described above exhibit a number of disadvantages. For example, when the automatic steering system is off, it is entirely possible that it could be switched on inadvertently by accidental manipulation of the operating switch. Conversely, when the steering system is on and an emergency should arise which requires that it be turned off, the driver must effect a conscious manipulation of the operating switch which delays the immediate switching-off of the automatic steering system in a potentially dangerous situation. This latter disadvantage applies, moreover, when the system is of a different known type wherein an emergency switch, which may for example be combined with the steering wheel knob, is mounted directly on the vehicle steering wheel to switch the automatic steering system off in dangerous circumstances. The operation of such emergency switches also requires quick reaction on the part of the driver. As a result, the speed with which the automatic steering system is switched off will vary in dependence upon the reaction time and readiness of the driver in an emergency situation.
As a rule, when an emergency condition arises which necessitates deactivating the automatic steering system, the initial unconscious reaction of the driver is to attempt to effect a steering correction by manual operation of the agricultural machine, since it is normally possible to steer the machine manually even when the automatic steering system is in its on condition. In general, however, due to the very rapidly operating regulation of known automatic steering systems, it is impossible, even with fast rotation of the steering wheel, to completely override the automatic steering system. The automatic power assists which are employed in such systems are usually stronger and quicker in operation than a manual operation, and a manually-effected correction is therefore almost immediately reversed. The present invention, recognizing these factors, makes use of the normal initial reaction of the driver to achieve deactivation of the automatic steering system, so that the driver can indeed immediately override the automatic steering system in an emergency situation.
The primary object of the present invention is, accordingly, to provide a switching mechanism operative to switch off the automatic steering system on a self-propelled agricultural machine, and a cooperating separate switching mechanism for switching on the automatic power system when it is appropriate to do so, which mechanisms operate in physiologically and psychologically practical manners to achieve an immediate switching off of the system when necessary, and which further operate to prevent the steering system from being inadvertently switched on when it is in its off condition, thereby to eliminate operating mistakes in the switching on and off of the automatic steering system.